1) Field of the Invention
The present invention relates to a technology for efficient integration of multimedia data.
2) Description of the Related Art
Recently, in accordance with the development in a network environment and a multimedia technique through the Internet, various systems have been realized. Among the systems, there is a video delivery system for delivering a video, which is a kind of multimedia data, to terminals of users.
Examples of the video delivery system include a remote video delivery system (a system that encodes a video photographed by an installed camera and delivers the video to viewer terminals through network transmission) and a mobile video delivery system (a system that delivers a video to portable terminals such as cellular phones).
It is conceivable that, in future, higher-order services are provided by combining these systems. More specifically, there is a system that accumulates videos at plural points, which are photographed by a large number of cameras arranged in a wide environment, in a video accumulation server arranged in each area and reconstitutes one video for portable terminals from the videos at the plural points to distribute the video to a portable terminal when delivery of the video is requested by the portable terminal. This system makes it possible to acquire videos in a wide area instantly regardless of time and place.
Such a system is promising from viewpoints of information transmission in the form of a video with an object of revitalization of a region, early preventive measures for disaster prevention, and the like. However, element techniques described below are required to realize this system.
First, when a video is delivered to portable terminals, it is necessary to convert accumulated videos managed by the video accumulation server into a data format with which the video can be referred to by the portable terminals. For example, compared with a general personal computer, a cellular phone has a smaller data size that can be treated as image data and has a different coding method. Thus, it is necessary to convert the coding method or the like to reproduce accumulated videos, which are stored in a high image quality, in the portable terminals.
In addition, to integrate videos accumulated in plural places under a wide environment to bring the videos into a deliverable state, it is necessary to provide a system that performs cooperative processing through network transmission between an integration server that creates a deliverable image and a video accumulation server that manages an object video.
More specifically, it is necessary to provide a system in which an integration server requests different plural video accumulation servers, which manage object images, to transmit a part of accumulated videos, and the plural video accumulation servers transmit videos required for integration through a network in response to the request.
In addition, to improve processing efficiency of the system, it is necessary to make video transmission over the network efficient. When a video required for integration is transmitted over the network, rather than transmitting the entire video to the integration server and extracting an object time slot in the integration server, a time slot is extracted in the video accumulation server in advance before the network transmission and only a part of the videos corresponding to the time slot is transmitted (see, for example, Japanese Patent Application Laid-Open Publication No. 2003-185304).
However, in the conventional method, there is a problem in that, since it takes time to regenerate a video for portable terminals, a significant delay occurs from the time when delivery of the video is requested until the time when the delivery is actually started. Thus, it is necessary to reduce a processing time until the video for portable terminals is regenerated. For this purpose, it is necessary to use calculation resources of respective servers constituting the system efficiently. In other words, it is necessary to perform appropriate distribution processing in the respective servers constituting the system.
Here, processing necessary until the video for portable terminals is generated includes slicing of videos, decoding, reduction in resolution, re-encoding, and integration. In the slicing of the videos, parts of the videos are sliced by a unit of time slot, for example, ten seconds out of a file consisting of videos for several hours. In the decoding, encoded accumulated videos are decoded. In the reduction in resolution, arithmetic processing is applied to the decoded videos to reduce a resolution to meet criteria in portable terminals to which the videos are delivered. In the re-encoding, the videos subjected to the reduction in resolution are re-encoded to be videos of a format corresponding to the terminals to which the videos are delivered. Finally, the videos in the plural points are integrated as one video by the integration to change the format to a file format with which the terminals, to which the video are delivered, can perform reproduction processing.
This processing is characterized in that an amount of calculation is larger in the decoding, the reduction in resolution, and the re-encoding compared with the slicing of videos and the integration. In addition, when the videos from the plural points are integrated, there are plural video accumulation servers to be objects of integration. Considering these respective kinds of processing as processing units, the processing up to the re-encoding is performed the number of times equivalent to the number of the video accumulation servers.
In other words, in the conventional method, the kinds of processing requiring a large amount of calculation, namely, the decoding, the reduction in resolution, and the re-encoding are performed on the integration server side with respect to all the accumulated videos at plural points to be objects of integration. Thus, that part of the processing is a bottleneck for the entire processing.
On the other hand, processing performed in the respective video accumulation servers is only the slicing of videos. Thus, after slicing the videos, the video accumulation servers performs no processing while the integration server performs the processing requiring a large amount of calculation. This means that calculation resources of the video accumulation servers after slicing the videos are not used well.
Thus, a method is conceivable in which, before transmitting a time slot of an object video to the integration server, the processing including the slicing, the decoding, the reduction in resolution, and the re-encoding of videos is performed in the video accumulation servers in advance, and only the integration processing is performed in the integration server. In this way, the decoding, the reduction in resolution, and the re-encoding, which are the kinds of processing requiring a large amount of calculation, are performed in the respective video accumulation servers. As a result, since the kinds of processing performed only in the integration server are distributed, the calculation resources can be used efficiently and a reduction in a processing time to some extent can be expected compared with the conventional method.
However, the method has a problem in that a total processing time depends on a processing time of a slowest video accumulation server, and an increase in delay due to the video accumulation servers, which require a longer processing time compared with other points, cannot be controlled. On the other hand, since processing that should be performed in the integration server is only the integration processing, a problem also occurs in that, contrary to the conventional method, calculation resources of the integration server is not used efficiently.